Neutralized short wave amplifier circuit



April 28, 1942. E. WILLWACHER a-rm.

' NEUTRALIZED SHORT WAVE AMPLIFIER CIRCUIT Filed Feb. 15, 1941 oRs- Ache:- Hem 6m RNEY Patented Apr. 28, 1942 r NEUTRALIZED SHORT WAVE AMPLIFIER CIRCUIT Erwin Willwacher and Heinz Gollub, Berlin,

Germany, assignors to Telefunken Gesellschaft I fur Drahtlose Telegraphie' m. b. H.,-Zehlendorf,

Osteweg, Berlin, Ger

Germany 9 Claims.

Neutralized amplifier circuits have been disclosed in the prior art, especially for ultra short waves (see United States Patent 2,222,423, grantedNovember 19, 1940, to E. Rahn et 2.1.), which offer the advantage over earlier circuit organizations that in the presence of unvaried (absolute or perfect) neutralization, that is .to say, complete freedom from reaction between output circuit and input circuit, it is possible to produce variable generation or damping of the amplifier tube. This insures far higher amplification or a substantial increase in the stability of the circuit organization-and avoidance of stray oscillations.

Neutralization, that is to say, freedom from reactions between input and output circuits of a tube arrangement is a general rule insured by the use of bridge schemes. In bridge schemes as before mentioned also freedom from feedbacks is insured; that is, freedom from reaction occasioned by the plate circuit upon the gridfilament circuit. This makes it feasible to vary this last mentioned feedback with the result that the circuit organization can be regenerated or damped at will, with neutralization as herein-'- before defined being maintained.

The present invention is particularly adapted to conditions surrounding decimeter wave amplification. It largely avoids and suppresses the v tendencies toward undesired oscillations in the circuit organization. The present invention comprises a symmetric circuit arrangement with two tubes, one of which (optionally) is unheated or is replaced by a simulation or equivalent scheme, the said symmetric arrangement being of such a nature that the plates are united by way of the output circuit; that from the plate of each tube to the grid of the other tube balancing condensers are brought, and that the -cathodes are united by way of impedances regulating regeneration or damping, while, finally, between the grid and filament points or terminals a four-terminal net'workor quadripole consisting of two balancing capacities and the input circuit symmetrically fitted and adaptedto the tube arrangement is provided.

The invention shallnow be described in more detail by reference to the accompanying draw-v ing, wherein: v

Figs. 1a and 2a show two different embodiments of the present invention; and

Figs. 1b and 2b show equivalent bridge arrangements for the circuits of Figs. 1a and ,2a, respectively.

Circuit organization Fig; 1a constitutes a demany, a corporation of Application February 15, 1941, Serial No. 379,068 I In Germany August 24, 1939 Lgi and Lgz is separated from the output end L's.

nected the input coils L92 and Lg; which are identical to each other. The input coil is split in order that regulationof regeneration by means of impedance Xi; may notupset outer neutralization.

Fig. lb shows the bridge 111; go; a2; K2; K1, by 4 which the input potential induced in-phase in.

For regeneration of the quadripole, the internal reaction at the active tube between 111-701 and gP-kl is decisive, and this is regulated by Xk.

Since for theinput potentials K1 and K2 are atlike potential, regulation Xk has no effect upon the input circuit. Hence, once the input circuit is tuned, this will neither be changed by later tuning of output circuit nor regulation of Xk.

A circuit organization comprising an inactive tube may be further expanded to result in the following push-pull arrangement with two active tubes, as shown in Fig. 2a. The input loop Lg according to Fig. 2a is inserted here between the grids of the tubes, regeneration being again adjusted by Xk. Fig. 2b shows that by the outer bridge 91, m, an, a2 input and output ends are isolated. The condition for balance is air ut C2 more particularly Q1=c2=Cga, wherein C is the grid-anode capacity. By equivalent balance of the inner bridge 91, ki, 92, k2 regulation of the regeneration by Xk is possible independent of the outer neutralization and the The condition is' input circuit.

stance be varied independently of the outer neutralization.

What is claimed is:

1. A neutralized amplifier circuit for ultra short waves comprising a pair of vacuum tubes each having a cathode, a grid and an anode, an output impedance connected between said anodes, a condenser connected between the anode of each tube and the grid of the other tube, a variable impedance connected between the cathodes of said tubes, a connection consisting of a pair of serially connected condensers between said grids, connections each including an inductance from opposite sides of said variable impedance to the junction point between said serially connected condensers, and means for applying input potentials to said inductances.

2. A neutralized amplifier circuit for ultra short waves comprising a pair of vacuum tubes each having 'a cathode, a grid and an anode, an output impedance connected between said anodes, a condenser connected between the anode of each tube and the grid of the other tube, a variable impedance connected between the oathodes of said tubes an inductance located between said grids, a condenser located between the grid of each tube and the cathode of the other tube, and means for applying input potentials to said inductance, whereby opposite polarities simultaneously appear on said grids.

3. A neutralized amplifier circuit for ultra short waves comprising a vacuum tube having a cathode, a grid and an anode, a network simulating the constants of said tube and comprising three spaced elements corresponding to the electrodes of saidtube, an output impedance connected between said anode and the corresponding element of said network, a condenser connected directly between the anode of said tube and that element of said network corresponding to the grid, a condenser connected directly between the grid of said tube and that element of said network corresponding to the anode of said tube, a variable impedance connected-between the cathode of said tube and the corresponding element of said network, and a four-terminal network, including an input circuit, coupled between said grid and its corresponding element and the cathode and its correspondingelement, said four-terminal network including a pair of balancing condensers directly connected to said grid and the corresponding element of said first network; V

4. A neutralized amplifier in accordance with claim 3, characterized in this that the relative positions of the elements of said first network are adjustable.

5. A neutralized amplifier circuit for ultra short waves comprising a pair of vacuum tubes each having a cathode, a grid and an anode, an output impedance connected between said anodes, a condenser connected between the anode of each tube and the grid of the other tube, a

variable impedance connected between the cath- ""odes'ot-sai dtubes. a connection. consisting of a pair or serially connected condensers between said grids. connections each including an I ductance from opposite sides of said variable impedance to the junction point between said serially connected condenserasaid inductances being similar and of equal value, and means for applying input potentials to said inductances.

6. A neutralized amplifier circuit for ultra short waves comprising a vacuum tube having a cathode, a grid and an anode, a network simulating the constants of said tube and comprising three spaced elements corresponding to the electrodes of said tube, an output impedance connected between said anode and the corresponding element of said network, a condenser connected directly between the anode of said tube and that element of said network corresponding. to 'the grid, an impedance connected directly between the grid of said tube and that element of said network corresponding to the anode of said tube, a variable impedance connected between the cathode of said tube and the corresponding element of said network, and afourterminal network, including an input circuit, coupled between said grid and its corresponding element and the cathode and its corresponding element, said four-terminal network including a pair of balancing condensers directly connected to said grid and the corresponding element oi said first network.

7. A neutralized amplifier. circuit for ultra short waves comprising a pair of vacuum tubes each having a cathode, a grid and an anode, an output impedance connected between said anodes, a condenser connected between the anode of each tube and the grid of the other tube, a variable impedance having opposite terminals connected tothe cathodes of said tubes, an inductance located between said grids, a condenser located between the grid of each tube and that terminal of, said variable impedance which is directly connected to the cathode of the other tube, and means for applying input potentials to said inductance, whereby opposite polarities simultaneously appear on said grids.

8. A neutralized amplifier circuit for ultra short waves comprising a vacuum tube having a cathode, a grid and an anode, a network simulating the constants of said tube and comprising three spaced elements corresponding to the electrodes of said tube, an output impedance connected between said anode and the corresponding element of said network, a condenser connected directly between the anode of said tube and that element of said network corresponding to the grid, a condenser connected directly between the grid of said tube and that element of said network corresponding to the anode of said tube, a variable impedance connected between the cathode of said tube and the corresponding element of said network, an inductance located between the grid of said tube and the corresponding element of said network. a condenser located between the grid of said tubeand that element of said network corresponding to the cathode, a condenser located between the cathode of said tube and that element of said network corresponding to the grid, and means for applying input potentials to said inductance,

whereby opposite polarities simultaneously appear on said grid and the corresponding element of said network.

- 9. A neutralized amplifier circuit for ultra short waves comprising a vacuum' tube having a a cathode, sand and an anode, a network simulating the constants of seid tube and comprising three spaced elements corresponding to the 6100-,

trodes of said tube, an output impedance connected between said anode and the corresponding element of said network, a condenser connected directly between the anode of said tube and that element of said network corresponding to the grid, a condenser connected directly between the grid of said tube andthat element of said network corresponding to the anode of said tube, a variable impedance connected between the cathode of said tube and the corresponding 10' 

